The invention relates generally to optics, and more particularly to multilayer optic devices and methods of making the same.
In X-ray based imaging and analysis applications, such as but not limited to computed tomography (CT) or X-ray diffraction, conventional X-ray sources generate a sufficient amount of X rays for imaging and analysis; however, more than 99% of the generated X rays travel in directions where these X rays are not utilized for the intended purpose. The unused X rays are absorbed by the source housing or primary X-ray beam collimator. Due to a large portion of generated X rays not being utilized for the intended purpose, existing X-ray imaging and analysis applications suffer from insufficiently low X-ray flux at the patient or sample being imaged or analyzed.
Currently, commercially-available optic devices capture and redirect typically 1% or less of the unused X rays from the source in desirable directions. Hence, these X rays remain unused even after employing commercially-available optic devices in the X-ray system. Prior and currently available approaches for increasing the X-ray flux on the patient or sample rely on increasing the number of X-rays generated in the source. The X-ray flux is typically increased by increasing the electron beam density impacting a target. Although this approach provides enhanced flux values, there is a physical limit to maximum number that can be produced this way that is imposed by the target materials. For example, when electrons impact the target and create X rays, if the heat generated is not dissipated quickly enough, the target will evaporate or melt. Moreover, by using this approach of increased electron beam density, the X-ray flux may be increased only by about 50 percent over current state of the art before target integrity is compromised.
In applications such as medical CT or X-ray diffraction (e.g., baggage scanning for explosives detection), the X-ray beam shape is not circularly symmetric. In such cases, the X-ray flux on a patient or sample may be increased by using multilayer total internal reflection (TIR) optics to redirect some of the “unused” X rays into one of the useful directions, such as a cone direction of the X-ray beam. Such collection and redirection of the X-ray beam in one direction is referred to as a one-dimensional compression and can result in intensity gains of more than several hundred times over the gains achieved by other optic devices. In several instances, for example cardiac CT imaging for reducing cardiac motion effects or fast baggage scanning using X-ray diffraction, it may be desirable to have even higher intensity X-ray fluxes.
It would thus be desirable to provide an optic device that can collect and redirect X rays in directions other than the cone direction and increase the intensity of the X-ray flux on the patient or the object.